Multi-stage carburetor



Filed May 13, 1955 lhmmi I H. A. CARLSON ETAL MULTI-STAGE 'CARBURETOR 6 Sheets-Sheet 1 FIG.I

. INVENTORS HAROLD A.CARLSON OLlN J. EICKMANN ATTORNEY Filed May 13, 1955 A Feb. 11, 1958 2,823,019

H. A. cARLsoN ET AL MULTI-STAGE CARBURETOR 6 Sheets-Sheet 2 HAROLD A. CARLSON OLIN J. EICKMANN ATTORNEY Feb. 11, 1958 H. A. CARLSON ET AL MULTI-STAGE CARBURETOR Filed May 15, 1955 6 Sheets-$heet 3 INVENTORS HAROLD ACARLSON OLIN J. EICKMANN WATTQRNEY I Fe'bu 1E W58 H. A. cARLsoN ET AL 2,823,019

MULTI-STAGE CARBURETOR Filed May 13, 1955 6 Sheets-Sheet 4 FIG.6.

ATTORNEY Feb. 11,. .1958 H. A. CARLSON ETAL 2,323,019

MULTI-STAGE CARBURETOR I Filed May 13, 1955 6 Sheets-Sheet 5 INVENTORS HAROLD A. CARLSON ATTORNEY OLIN u. EICKMANN .MULTI-STAGE CARBURETOR Harold A. Carlson, Brentwood, and 01in J. Eickmann, Normandy, Mo., ass'ignors, by mesne assignments, to ACE Industries, incorporated, New York, N. Y., a corppration:ofNew..Iersey .Appllication May, 13, 1955 Serial No. 508,039

7-Claims. (Cl. 261'23) Thisiuvention :rjelatesto multibarrel or. multi-stage carburetorsystems;v for internal combustion. engines. .More; particularly, thezinvention relates to a novel combinationiof afuel rsupply and1a new fuel nozzle system for..:such carburetors which eliminatesthe necessity of two separate fuel .howsl :and of four separate-nozzle systerns.v

The invention:is:shown:applied to the type of lcarburetor disclosed in iPatentNo. 2,715,522, issuedAugust 16, 1955;, toiCarlson and Moseley. Briefly, this prior application shows a multi-barrel, multistage carburetor with' four barrels and four separate floatchambers, which chambersare connected in pair-sto'form two fuel bowls, each supplying ifuelto two individual fuel nozzle systems.

The performance of carburetors with multiple fuel bowls and nozzle systems is not wholly satisfactory because they cannot -be readilycalibrated for changes in acceleration, cornering, braking, or inclination 'of the-vehizolev :Such': changes can produce an-uneven distribution of fuel with its accompanying disadvantages in engine performance.- Furthermore, the transition point. which occurs when the secondary stages go intoaction is very pronounced, and-is regarded, for that'reason,,as undesirable.

In-t he present invention, two float chambers are .interconnected-by a restricted passage to form. a single fuel bowls. This bowl supplies fuel to two separate fuel -noz.- zle systems of novel design'one for *each pair ofprimany and secondary stagesof the multi-barrel, multistage-carburetor. The location of the point .of 'supply,for each nozzle system is adjacent one side of the fuel bowl, preferably from awzonelocated in the. restricted passage connecting the float chambers. Eachfuelfsystem hasa conventionally arranged low-speed nozzle or idling ports supplied with fuel through passages connecting with a main inclined fuel passage from the point of supply withinjthe .fuel bowl. The main or high-speed primary and secondary. nozzles are in a tube extending transversely of the primaryand secondary stage barrels. This tube, in turn,- connects with the inclined main fuel passage from the fuelwbowl. The junction between the tube and the passage. forms a single control point for both primary and secondary stage fuel nozzles, and this control point ispurposely located adjacent the volumetric center of the fuel bow l above the liquid level. Each fuel nozzle has one or more air bleeds at a point in a zone pressure-sensiti-veto throttle positions.

The combination of a single fuel bowl with two fuel nozzle systems has been found to avoid .unequal distribution-of fuel, and its disadvantages. This is -due.to the proximity of the fuel supply for each fuel nozzle system, and 'to the feature of having a single control point for each pair of main or high -speed nozzles. Because of the single control, point, the amount of lift from the fuel bowl togeach' primary and secondary stage main nozzle is identical under the conditions above mentioned which occur due to accelerations or inclination of the vehicle.

nited States Patent.

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Furthermore, the interconnecting air bleeds provide a smoothtransition fr om :primaryto secondary stage by enriching *the mixture in the primary stage to compensate for the additional 'air admitted through the secondary stage before thesecond'ar-y stage fuel nozzle begins to function.

This application is a continuation in-par t of an I allowed application-of Carlson and Eickmann, Serial No. 3'4'5i048, filed -March 27 19 5'3;--for MuIti-Stage Carburetor, now Patent No. 2,718,387, issued Septeniber'ZO, 1955;

The accompanying 'drawings illustrate several *forms of the instant invention.

Fig; 1 is a top plaa view of acarburetor according ffO the present invention;

Fig; 2 is -'a verticalffrorit elevational view of "thecar- 'buretor-with" parts "broken 'awayto show the adjacent points "of 'fu'el s'u pply to the 'fuel'nozzl'e systems within the fuel bowl. I

Fig; 3 'is -a'-si'de' elevationalview of the carburetor with parts broken --'away to illustrate a float chamber and its float control mechanism.-

Fig; -4 is avert'ical longitudinalv section. through the carburetor.-

Fig: '5 is a detail view of the. choke valve-operated mechanism for locking out the action of the throttles for the secondary stages.

Fig; '6 is 'a/longitudinalsection illustratinga modification of the present 'finvention.

'Fig. 7 isa diagrammatic view illustrating the lack of eifect of changes in inclination of xtheve'hicle on the relationbetween the fuel level in the fuel bowl and the .contro'lpoint for the fuel nozzle.

.Fig. 8 *is a longitudinal; section illustrating a modification of ,the nozzle sh'ownin Fig.4.

Fig, 9' is a longitudinal section through acarburetor illustrating .still another modificationiof the invention.

The drawings, illustrate a .four-barreldowndraft car.- bure'tor with a body 10'. As. s'howninQ-Fig; :1, this.lbody includes two forward ornprimary, stage .mixtureconduits 11" and 12, and two" rear or. secondary stagenriixture conduits,13 land 14.- These conduits are arranged. insymmetr'ica'llrelation in a. compaotgroup,,.and aresupplied with air througha rectangular-shaped,airfhornstructure 15 provided with .,a .transverse partition '16.. At the forward s'ideof the partition. is :journaleda chokes'haft .17 mounting an unbalanced choke valve.18."(see.f1?ig. 4,). Thechokeshaft isrcontrolled by any suitable automatic choke. control mechanism.,.within .ithe. housing19 in .Fig. 2. Extending across :both. primary, and secondary mixture, conduits. are .throttlecshaftslfl.and 21 mounting throttle valves .2 2, and 23. Each pairuofpr imary. throttles 22 movesas annitr, Likewise,. each pair'ofsecondary throttles ,23. moves as aunit. The primaryconduits may bejconnectedjby pressurerequalizing,passages, and the secondary conduitsdmay; be. likewise .connected, if desired... A flange 26:.s'urrounding.theslowerend-of the conduits is provided for attaching the carburetor to theiusual engine. intake manifold.

Referring to Figs. ;.2,and 5 the .primary throttle shaft 20. has a projection onwhichwis .rigidly mounted a throttle operating arm .27 having a.ho1e 28. for.attachment to the usual accelerator linkage; Th6 .th1i0ttl6 arm carries .an adjustingscrew. forengaging atfast idle cam .39 pivoted as at31 tothe.carburetor/body The camisconnected by a torsion. .s,pring ,32;..to a.concentrically-pivoted tloose lever 33, which, in turn, is connected bymeans of a link 34,;to anarrn 351igid..with: the-1 projecting extremity of choke valveshafit :11, whiohis .located oppositesaid hous ing 19 A ;small .d-isk..36.is rigid with the adjacent pro jecting extrernity of. agsecondary throttle shaft 21, and has a radiallugfifia. Alsoloosely mountediwith respect to the pivot element 31 is an eccentrically weighted stop lever 37 provided with a finger 38 which is normally maintained by its own weight in position to interfere and engage with lug 36a on the secondary throttle shaft 21 when the choke valve is closed. This lock mechanism is the same as that shown in Patent No. 2,715,522, issued August 16, 1955, to Carlson and Moseley. It is explained therein that lug 39, which is integral with lever 33, will engage eccentrically weighted lever 37 as the choke valve moves toward opening position, thereby shifting the lever 37 to unlock the secondary throttles 23 by its disengagement with the lug 36a.

The mechanism for operating the primary and secondary throttles in a sequential manner is shown in Fig. 3, and this mechanism comprises a small lever 100 fixed with primary throttle shaft 20, which lever is formed with radial and angularly extending lugs 101 and 102. A lever 103 is rotatably mounted on throttle shaft 20 inward of lever 100, and has a finger 104 connected by a coil tension spring 105 to the finger 101 of the operating lever 100. Spring 105 normally maintains a second integral finger 102 in engagement with lug 106. Lever 103 has a second angular lug 107 mounted thereon for a purpose to be later described. Also rotatably mounted on the throttle shaft is a third lever I08 inwardly of fixed lever 100 and lever 103. This lever is connected by a link 109 to an arm 110 rigidly secured with the adjacent projecting extremity of secondary throttle shaft 21. Arm 110 may be biased in a counterclockwise direction by a suitable torsion spring 120 or the like. counter-clockwise movement of the shaft 20 to open the primary throttles 22 moves lever 100, and lever 103 is likewise rotated through spring connection 105 until radial lug 107 engages a shoulder 113 on third lever 108, whereupon the three levers rotate as a unit, causing opening of the secondary throttles 23 by link 109 and arm 110. Because of the lost motion connection between lug 107 and shoulder 113, primary throttles 22 are in a partially opened position before engagement between lug 107 and shoulder 113 causes initial movement of the secondary throttles. The linkage is such, however, that movement of the primary throttles from this partially open position to wide open causes full opening of the secondary throttles. Upon closing of the primary throttles, the aforementioned spring which may be used on the secondary throttles causes the secondary throttles to follow the movement of the primary throttles. Full closing of the primary throttles engages shoulder 114 with lug 115 to lock the secondary throttles in a closed position.

Of course, if the choke valve-operated lock-out mechanism previously described is in operation, the secondary throttle cannot be opened, and spring 105 will allow for movement of the primary throttles in an opening direction after engagement of lug 107 with shoulder 113.

- As shown in Figs. 2 and 3, the carburetor is provided with a fuel bowl having two identical float chambers 40 and 41. (A description of one will suffice for both.) These chambers are interconnected by a restricted passage in which is located the supply point for two fuel nozzle systems.

Float chamber 40 contains a float 42 mounted on a float control arm 43 pivoted on a shaft 44 supported by structure depending from float bowl cover 46. Finger 45 on arm 43 engages and actuates a needle valve 47, which, in turn, controls the supply of fuel past valve seat 48 from a common inlet 49 for both chambers 40 and 41 shown in Fig. 1. Float 42 and needle valve 47 maintain a substantially constant fuel level within the fuel bowl 4041.

The passage between the float chambers 40 and 41 has two metering orifices 50 and 50' located in the lower portion thereof. Each is, in turn, controlled by metering pins 51 and 51' carried at the upper end by a cross-bar 52 shown clearly in Figs. 1 and 2. This cross-bar is formed as an integral part of a stem 53 projecting upwardly from In operation,

a piston 54, which works in a cylinder 55 connected by means of a passage 56 to the primary mixture conduit posterior of the throttle 22. A coil spring 57 constantly urges the piston and metering pins upwardly against the force of suction acting downwardly on the piston.

Journaled in the fuel bowl cover 46 is a countershaft 58 which mounts an actuating lever 59 having a finger 60 underlying the cross-bar 52 so as to lift the cross-bar and metering pins when the countershaft is rotated. The countershaft, in turn, is connected to the primary throttle valves by an actuating arm 61 rigid with the projecting end of the countershaft 58 and a link 63 connected to throttle lever actuating arm 27.

Also attached to the countershaft is a lever 65 which is connected by a small link 66 to an accelerating pump piston not shown. This piston works in the usual cylinder. and draws fuel into that cylinder on upward movement of the piston. Upon opening movement of the accelerator, the fuel is discharged from the cylinder of the pump past suitable check valves and into the primary mixture conduit through pump jets 76, all in a well known manner, as shown in the co-pending application to Otto Henning, Serial No. 268,811, filed January 29, 1952, now Pat. No. 2,728,563, dated Dec. 27, 1955. The mechanism just described is mounted under a dust cap 62 as shown in Figs. 1 and 2.

The main fuel supply from each fuel bowl to adjacent primary and secondary mixture conduits is through individual fuel nozzle systems which are identical. Consequential, only one fuel nozzle ssytem will be described. In Fig. 2, fuel through the metering orifice 50 is supplied to a main fuel passage 77 through a connecting passageway. Passage 77 is inclined upwardly as shown in Fig. 4, and connects with a fuel tube 78 extending across and between inner venturi tubes 79F and 79S in the primary and secondary conduits. Tube 78 has fuel ports'80 and 81 in these venturi tubes, respectively, and air bleed openings 82 and 83 more or less in alignment therewith. A vertical passage 84 connects between a port 85 adjacent the secondary throttle and a restriction 86 in the fuel tube 78. The main fuel system also includes a combination air bleed and vapor vent orifice 87 connecting with the inclined fuel passage 77.

. Idling fuel nozzles are provided for each primary mixture conduit. These are identical, and a description of one will suffice for both. This idling system has a vertical well 90 containing an idling tube 91 which connects through a series of passages 92 with idling ports 93 and 94 adjacent the primary throttle 22.

Operation With the primary throttle 22 in idle position and the secondary throttles 23 closed, fuel is supplied to the separate idle nozzles in the separate primary mixture conduits from the fuel bowl 40, 41 through the metering orifices 50, 50, inclined passages 77, and idle tubes 91,

to the idle ports 93 and 94. As the primary throttles are opened, suction gradually increases in the inner venturi tubes 791, which produces a flow of fuel through the fuel tubes '78 and then to and through discharge nozzles 80. Simultaneously, suction decreases at the idle ports and a gradual transition takes place until nozzles supply all of the fuel. The action of suction on the fuel nozzles 80 is somewhat modulated by the leakage of air at atmospheriopressure through the ports 81, 82, 83 and into the fuel tubes 78 when the throttles in the secondary mixture conduits are closed. This modulating effect of the air bleeds reduces the discharge from nozzles 80 to vgive a proper mixture for part-throttle operation.

When the primary throttles are opened far enough to begin opening the secondary throttles 23, then suction will exist in both the primary and secondary inner venturis 79F and 798, which will reduce the amount of air bleed through ports 81 and 83, and thereby increase the rate of fuel flow into the fuel tubes 78 in order to initially increase the amount of fuel tothefueh nozzles. 180.5. Fur ther. opening of ;.the. secondary. throttles: :increasesdhe suction at ports, 81 and; 83tolfurtherincreasetheflow through tubes 78 to supply sufiicientfuel for.- boththe primary and secondary nozzles. Duringtthetinitial opening of the secondary throttles 23,-;ports 85,,- initially wholly anterior thereto, will be, gradually exposed-to'manifold suction, which, in turn, Will: decrease the effectiveness, .of these air bleeds. and increase the amount of fuel delivered to enrich the mixture in .the primary stages..-g Butsthis invention contemplates the. use..of..the.-device with or without the ports, 85.: Thefunctionwould .be-the same regardless of their presence orabsence.

Another advantageivbesides those; which; are obvious and flow directly from thesimplification ofthe mechanism, resides primarily inthe feature of providinga carburetor of this type wherein the fuel is, lifted ;a constant amount, regardless of tip angle. In;Fig. 7,-for. example, if the carburetor is tipped backwards due to ,a steep ascent, theamount of lift necessary to get the fuel toboth the primary and secondary nozzles remains the same, as illustrated by intersectionpof lines xx and .n..n,; the latter being the normal fuel level. This. is fixed by the fact that the distance from thefuel levels nn and, xx tothe intersection of passage, 77 with the, fuel tube 78 remains substantially constant because. thecontrol ,point at the interscctionis located vertically above and substantially centrally of the fuel chamber 40. Consequently, the amount of lift due to tipangle is unchanged. Because of this, the carburetor will operate, as, satisfactorily at an inclination as at a level position. If: the carburetor is tilted the other way (or forward, as illustrated'by line y--y), the lift also remains unchanged. Thesecondary fuel nozzle will be ;above the primary, but this. would only be in descending a steep, grade, when it is very unlikely that the secondary throttle would be held-wide open and when a leaner mixture in the sec-v ondary stages is desirable anyway.

Fig. 6 shows a modification of thejnvention described above in which metering rods are provided in each-of the mixture conduits for operation with the-fuel ports in the fuel tubes. In-thismodification, four metering rods 151 are received inthe fuel ports 80, 81, respeetively. The rods are pivotally connected; at 152 with arms 153 mounted on the throttles 22 and 23, respectively.- Meter.- ing rods 151 are provided with stepped ends 154 received in the fuel ports 80, 81, and air bleed orifices 82,-83.

In this modification, with only the primary throttles open, flow from the ports'80, 81 is controlled by the metering rods received therein. Because suction will exist only at the primary nozzle, the mixture is also controlled by the amount' of air admitted by the metering rods 151 in the secondary-nozzles through the ports;8 1, 83,85. After the secondary throttles open, suction will exist inboth the primary-and secondary nozzles and port 85 will-aid-in-lifting the fuel from the bowl.- This will increase flow sufliciently to provide adequate fuel in both the primary and secondary nozzles. However, this invention contemplates the omission of port 85. Of course, the metering rod for the secondary cannot open until secondary throttle 23 is unlocked by opening of choke valve 18.

Fig. 8 shows a modified form of the invention illustrated in Fig. 4. The main fuel supply from each fuel bowl to adjacent primary and adjacent secondary mixture conduits is through individual fuel nozzle systems which are identical. Consequently, only one fuel nozzle system will be described. The same reference characters will be used to indicate corresponding parts. As described heretofore in Fig. 2, the fuel entering through the metering orifice 50 under control of the metering rod 51 supplies the main fuel passage 77 through a connecting passageway. Passage 77 is inclined upwardly as shown, in Fig. 8, and connects with a short fuel tube or secondary. barreln. Fueltzis-tsuppliedg to;-.the; secondary nozzle .181 from.,the.-inclined-.passage 77 ;byatube 179 connected with the. opposi-tegend 8f: :the fuel: tube 178.

The fuel flow. .t0;the secondary .fuel; nozzle 181 =is controlled bycmeteredt;orifices;;;169-;-.at:;the,lower end of inclined; fuel tubes .179;

In=:-.this arrangement; of-Jparts; thje fuel; supply to 1 both theprimary nozzle.;-180,-.;an d. the secondarynozzle 181 is metered at a. commonfpoint byta singlev metering orifice Silicontrolled by .thesmeteringz-rod51.1 Thisis a distinct advantage, due to theobvious simplific ti n and l mination .of. parts. Duringoperationwof;the primary :stage, when the throttle ,22 .;is 01 6 1; fuel will. bel.;supplied 1 from i the fuel bowlsv through the ,meteredjorificeSO to-the main fuel nozzle,.-180.in theprimary side, of; the,. carburetor. The operation of the .primary ;mai n-;;nozzle. will be bled out through two sources, 87.- and -181. Atmospheric pressures enteringat these POiIlt;;Wlll mix with the-fuel within the main fuel supply passage 77 so as to lean out the mixture to the proper proportions; fora-operation. on the primary barrelsof the carburetor.;;

Asgthe secondary throttlesu-23fbegin to open in the final; range .of-movement; of the throttles 22, the first effect is to enrich ,themixturefromthe primary nozzles 180 dueto the drop. in pressure created in the secondary venturi-79S at the ,openings-181 -of,the fuel-tubes 178.

This. action will compensate for the immediate' lack of I fuel in the nozzles-.181 andthe leaning out effect caused at this time by .thepassage of air. through the secondary barrels of the carburetor. When. .thenozzles 181 begin to-deliver fuel, whicha.the.y.will in due .course .if the throttles 23 'are held.open,=the supplyof fuel to the primarynozzles .180 through the metering orifices 50 will be decreased by an amountequalto that. delivered by the secondary nozzles 181. This will automatically com, pensate for the temporarily rich" condition in the primary nozzles 180.

Fig. 9 shows anothermodification of theinvention illustrated in Fig. 4. As in the above-described. illustrations, the main fuel supply from 'each'fuel-bowl to adjacent primary and adjacent secondary mixture conduits is through individual fuel nozzle systems-'which-are identical. Consequently, only one fuel nozzle will be described, and the same reference characters Will be used, where possible, to indicatelike parts. As stated in the description of Fig. 4, the bleed 85 and itsconnecting passage 84 maybe omitted if desired. Fig. 9shows-=a modification omitting this-construction. Since the nozzle arrangement of Fig. 9 is identical with that of -Fig. 4 in other respects,-thedescription thereof will not be repeated.

The choke valve 18=in the primary barrels of the'carburetor 10 carries a bracket *which, in turn, is pivotally connected to a metering rod 192 by a link 191. The rod 192 is received within a well 193 in the carburetor body and passes through a metering jet 194 in the fuel tube 78. It will be apparent that, with this construction, when the choke valve 18 is in operation, metering rod 192 will be positioned to cut off the air-bleeding effect produced through the ports 81 and 83 in the secondary stage. Consequently, the primary stage can be separately calibrated for proper operation of the choke valve 18. The final opening movement of the choke valve 18 will withdraw the metering rod 192 so as to open communication between the nozzles 81, 83 and the fuel passage 77. Under these conditions, the carburetor action will be similar to that described for Fig. 4.

This invention may be modified as will occur to those skilled in the art, and the exclusive use of all modificafl tions as come within the scope of the appended claims is contemplated.

We claim:

1. In a multi-stage carburetor, primary and secondary mixture conduits, primary and secondary throttles, respectively, controlling said conduits, a fuel bowl, a floatoperated valve for controlling the fuel supply to said bowl, a fuel metering orifice adjacent one side of said bowl, a main fuel passage from said orifice to a control point above the fuel level and adjacent the center of said fuel bowl, a fuel tube connecting with said passage at said control point and extending transversely through said primary and secondary mixture conduits, and a fuel nozzle in said tube for each mixture conduit, whereby a substantially constant relation is maintained between the fuel level and said control point to supply each said nozzle uniformly on inclination of said carburetor, and valve means provided in said tube between said nozzles to control the flow of fuel to said secondary conduit.

2. The combination defined in claim 1 in which said valve means is moved from closed to open position re sponsive to movement of a choke valve from closed to open position.

3. in a multistage carburetor, primary and secondary mixture conduits, sequentially operated primary and secondary throttles in said primary and secondary mixture conduits, primary and secondary fuel nozzles in said primary and secondary mixture conduits, a choke valve anterior of said primary nozzle, means for restricting secondary throttle opening movement when said choke valve is closed, and a fuel supply system for said nozzles comprising, a constant level fuel chamber, a main fuel passage, a fuel metering device between said chamber and said passage, a connection between said passage and'said nozzles, a metering device for said secondary nozzle, and means for maintaining said metering device in flow restricting position when said choke valve is in closed position and for moving said device to decrease the restricting effect.

4. In a multi-stage carburetor, primary and secondary mixture conduits, sequentially operated primary and secondary throttles in said primary and secondary mixture conduits, primary and secondary fuel nozzles in said primary and secondary mixture conduits, a choke valve anterior of said primary nozzle, and a fuel supply system for said nozzles comprising, a constant level fuel chamber, a main fuel passage, a fuel metering device between said chamber and said passage, a connection between said passage and said nozzles, a metering device for said secondary nozzle, and means for moving said device to flow restricting position in response to closing movement of said choke valve for lessening the effect of back-bleed from said secondary nozzle so as to increase the fuel delivery rate from said primary nozzle when said choke valve is closed.

5. In a multi-stage carburetor, primary and secondary mixture conduits, sequentially operated primary and secondary throttles in said primary and secondary mixture conduits, primary and secondary fuel nozzles in said primary and secondary mixture conduits, a choke valve anterior of said primary nozzle, and a fuel supply system for said nozzles comprising, a constant level fuel chamher, a main fuel passage, a fuel metering device between said chamber and said passage, a connection between said passage and said nozzles, and a metering device for said secondary nozzle operated in response to closing movement of said choke valve for lessening the effect of back-bleed from said secondary nozzle so as to increase the fuel delivery rate from said primary nozzle.

6. In a multi-stage carburetor, primary and secondary mixture conduits, sequentially operated primary and sec ondary throttles in said primary and secondary mixture conduits, primary and secondary fuel nozzles in said primary and secondary mixture conduits, a choke valve anterior of said primary nozzle and a fuel supply system for said nozzles comprising, a constant level fuel chamber, a main fuel passage, a fuel metering device between said chamber and said passage, a connection between said passage and said nozzles, a metering device in said connection to said secondary nozzle, and means for maintaining said metering device in a flow restricting position when said choke valve is closed for lessening the efiect of back-bleed from said secondary'nozzle so as to increase the fuel delivery rate from said primary nozzle 7. In a multi-stage carburetor, primary and secondary mixture conduits, primary and secondary throttles, respectively, controlling said conduits, a fuel bowl, a floatoperated valve for controlling the fuel supply to said bowl, a fuel metering orifice in the lower part of said bowl, a main fuel passage from said orifice to a control point above the fuel level and adjacent the middle of said fuel bowl, a fuel tube connecting with said passage at said control point and extending transversely through said primary and secondary mixture conduits, and primary and secondary fuel nozzles in said tube for the respective mixture conduits, whereby a substantially constant relationship is maintained between the fuel level and said control point to supply each said nozzle uniformly on inclination of said carburetor, and means including an orifice, a choke valve, and a metering rod operatively connected to said choke valve and movable Within said orifice for restricting the flow of fuel to said secondary nozzle.

References Cited in the file of this patent 

